Method and apparatus for manufacturing packaging bags, and bags obtained thereby

ABSTRACT

The present invention relates to a method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the stepsof forming respective cutouts ( 150, 160 ) in each of the two lateral, bellows-forming zones of a packaging bag sheet ( 100 ) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and heat-sealing ( 184, 186 ) the adjacent edges of the sheet to the peripheries of the cutouts ( 150, 160 ) to close the bag. The invention also provides apparatus for implementing the method and bags obtained thereby.

FIELD OF THE INVENTION

[0001] The present invention relates to the field of bags for packaging.

BACKGROUND OF THE INVENTION

[0002] Numerous packaging bags and numerous systems for manufacturingthem have already been proposed.

[0003] For bags of small thickness, those that are generally flat in thefilled state, known means generally provide satisfaction. Under suchcircumstances, the bags are generally formed using two planar sheetsthat are bonded together along three sides and that are provided withclosure means, for example complementary male/female strips, at themouth of a bag.

[0004] In contrast, until now, manufacturing bags that are intended toreceive contents that are thick, has turned out not to be entirelysatisfactory, even though a large amount of research has been performedin this very specific field.

[0005] In particular, such bags often require lateral bellows which aredifficult to make.

[0006] Accompanying FIG. 1 shows, diagrammatically, a known techniquefor manufacturing bags with lateral bellows by inserting pre-formedbellows 10 between two sheets 12 and 14 that constitute two main facesof the bags, with the bellows being inserted at 90° to the traveldirection S of the sheets 12, 14. The sheets 12 and 14 are provided withlongitudinal male/female closure strips 13 and 15. The bellows 10 arepreferably of varying width, increasing away from the closure strips 13and 15 so as to enable the bags to be inflated. That known techniquedoes indeed make it possible to manufacture packaging bags havinglateral bellows. Nevertheless, it turns out to be quite complex. Inparticular, the need to insert the bellows 10 at 90° to the traveldirection of the sheets 12 and 14 does not enable high manufacturingthroughputs to be obtained, and requires insertion of the bellows 10 tobe adequately synchronized with the travel of the sheets 12 and 14.

[0007] Document FR-A-2 686 063 describes another technique ofmanufacturing packaging bags with bellows that consists in preforming abag with lateral bellows, in splitting the bag over a portion of itslength along fold lines external to the bellows, in folding the flapsdefined in this way back over the outside of the bag, in placing theclosure strips on the flaps, in reforming the bag, and in bonding theclosure strips to the flaps that have been put into place.Unfortunately, because of its complexity, that technique does notprovide full satisfaction.

[0008] The Applicant has also described various alternative solutionsfor manufacturing packaging bags with lateral bellows in French patentapplication No. 96 02389 filed on Feb. 27, 1996.

OBJECT OF THE INVENTION

[0009] The present invention now seeks to improve known means formanufacturing packaging bags having lateral bellows.

SUMMARY OF THE INVENTION

[0010] The foregoing object is achieved in the context of the presentinvention by a method of manufacturing packaging bags comprising thesteps of:

[0011] providing a packaging bag sheet, having a longitudinal extent,for forming a packaging bag;

[0012] folding said packaging bag sheet so as to form a pair oflaterally spaced bellow regions within side edge portions of saidpackaging bag sheet;

[0013] forming cutouts within each one of said pair of laterally spaced,bellow regions of said packaging bag sheet so that saidbag has only twosheet thicknesses superposed with respect to each other within a mouthregion of said bellows

[0014] placing complementary male/femelle closure strips provided with acontrol cursor upon said packaging bag sheet within the vicinity of saidmouth region of said bag and transversely with respect to saidlongitudinal feeding direction and

[0015] heat-sealing edges portions of said sheet edge portions of saidcutouts so as to close and seal said bag.

[0016] In the context of the present invention, the complementarymale/female closure strips are preferably provided on respective mainsupport walls which are adapted to be fixed on the packaging bag sheetand which are connected together by an auxiliary wall adapted to bebroken when the bag is opened the first time.

[0017] The present invention also provides apparatus for implementingthe method, and bags obtained thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other characteristics, objects, and advantages of the inventionwill become apparent upon reading the following detailed description andupon looking at the accompanying drawings, given by way of non-limitingexample and in which like reference characters designate like orcorresponding parts throughout the several views and wherein:

[0019]FIG. 1, described above, is a diagram showing a conventionaltechnique of manufacturing packaging bags having lateral bellows;

[0020]FIG. 2 is a top plan view which shows a first step of a method ofthe present invention consisting in forming two Z-folds in a film;

[0021]FIG. 3 is a cross-section view through the film of FIG. 1;

[0022]FIG. 4 is a view similar to FIG. 2 and shows the portion of filmthat is removed to form cutouts;

[0023]FIG. 5 shows the film of FIG. 4 as provided with cutouts, whenspread out flat;

[0024]FIG. 5a is a similar flat view of a variant film of the presentinvention that is provided with cutouts;

[0025] FIGS. 6 to 9 show four successive steps of the method of thepresent invention for forming bags;

[0026]FIG. 10 is a schematic view in perspective of a cursor of thepresent invention,

[0027]FIG. 11 is a longitudinal cross-section view of the cursor throughthe section plan referenced XI-XI on FIG. 10,

[0028]FIG. 12 is a first transverse cross-section view of the cursorthrough the section plan referenced XII-XII on FIGS. 10 and 11 and

[0029]FIG. 13 is a second transverse cross-section viewof the cursorthrough the section plan referenced XIII-XIII on FIGS. 10 and 11.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0030] In FIG. 2, there can be seen a film 100 provided with two Z-folds110 and 120 that are parallel to the longitudinal direction D of thefilm 100.

[0031] The two Z-folds 110 and 120 can be formed by any appropriatemeans.

[0032] Each of them is preferably formed by means of two blades 200, 202or 200,204 that are superposed with partial overlap, as shown in FIG. 3,so as to form a baffle into which the film 100 is engaged.

[0033] The folds 110 and 120 are designed to form the lateral bellows ofthe bag once it has been completed.

[0034] After the folds 110 and 120 have been made, the film as shown inFIG. 2 has a planar main face 130 that is to form a main face of the bagafter it has been completed. On its longitudinal edges, this main face130 is extended on either side by first longitudinal flaps 112 and 122which are themselves extended by second longitudinal flaps 114 and 124.The flaps 112 and 114 form the fold 110. The flaps 122 and 124 form thefold 120. The flaps 112 and 122 are connected to the main face 130 bymeans of fold lines 111 and 121. The flaps 112 and 122 are foldedtowards the middle of the face 130 from the fold lines 111 and 121 sothat they underlie the main face 130. The flaps 114 and 124 areconnected to the flaps 112 and 122 by means of fold lines 113 and 123.The flaps 114 and 124 extend outwards from the fold lines 113 and 123.The flaps 114 and 124 are also of the same length as the flaps 112 and122 so as to underlie them respectively, being immediately beneath them.Finally, each of the flaps 114 and 124 is extended outwards by auxiliarysegments 140 and 142. These auxiliary segments 140 and 142 are designed,in combination, to form the second main face of the bags. As shown inFIG. 2, the two segments 140 and 142 are preferably of identical width.Nevertheless, this condition is not essential. What is essential is thatthe segments 140 and 142 possess a total width that is slightly greaterthan the width of the face 130 so as to form the second face of the bagsafter they have been folded about their outer longitudinal free edges,as explained below with reference to FIG. 8.

[0035] After the step of forming the folds 110 and 120 as shown in FIG.2, the flaps 114 and 124 are substantially coplanar with the segments140 and 142. The flaps 114 and 124 are connected to the segments 140 and142 by means of lines 115 and 125.

[0036] As mentioned above, according to an essential characteristic ofthe present invention, the method of forming a bag includes a step ofcutting out pairs of cutouts 150 and 160 at regular intervals in each ofthe zones that is to form a lateral bellows.

[0037] The areas of material removed to form these cutouts 150 and 160are shaded in FIG. 4.

[0038] The cutouts 156 and 160 are shown in the deployed state in FIG.5.

[0039] Finally, the cutouts 150 and 160 are shown in their realconfiguration within the folds 110 and 120 in FIG. 6.

[0040] The cutouts 150 and 160 can be formed in the film 100 beforemaking the folds 110 and 120. Under such circumstances, their initialshape is as shown in FIG. 5.

[0041] Nevertheless, it is preferable for the cutouts 150 and 160 to beformed after the folds 110 and 120 have been made. The cutouts 150 and160 can be made in the film 100 by any appropriate means. The cutouts150 and 160 are preferably made using the blade 200 as an anvil thatco-operates with a cutting-out punch so as to leave the face 130 of thefilm intact.

[0042] The shapes of the cutouts 150 and 160 can vary in numerous ways.

[0043] The cutouts 150 and 160 preferably extend between the lines 111and 115 on one side and the lines 121 and 125 on the other side, asshown in FIG. 5. Nevertheless, in a variant, as shown in FIG. 5a, thecutouts 150 and 160 can be formed so as to be set back from theabove-mentioned lines 111, 115 and 121, 125, as shown in FIG. 5a.

[0044] More precisely, and as shown in the accompanying figures, each ofthe cutouts 150 and 160 is defined by two longitudinal edges 152, 154and 162, 164, and by two transverse edges 156, 158 and 166, 168.

[0045] The longitudinal edges 152, 154 and 162, 164 are rectilinear andcoincide respectively with the lines 111, 115, 121, and 125 in FIG. 5,which lines themselves constitute the final outer generator lines of thelateral bellows, In the folded state as shown in FIG. 6, the pairs ofedges 152, 154 or 162, 164 are superposed.

[0046] The transverse edges 156 and 166 that are closer to the mouth ofthe bag are preferably rectilinear, extending transversely relative tothe longitudinal direction D of the film 100.

[0047] The second transverse edges 158 and 168 that are closer to thebottom of a bag are preferably not rectilinear, being concave towardsthe mouth of the bag. More precisely, the second transverse edges 158and 168 are preferably in the form of a dihedral made up of tworectilinear segments 158 a, 158 b or 168 a, 168 b. The above-mentionedpairs of segments 158 a, 158 b and 168 a, 168 b constituting respectivesecond transverse edges 158 and 168 are preferably identical in length.They extend respectively over the flaps 112, 114 and 122, 124. In thisway, the segments 158 a, 158 b and 168 a, 168 b intersect on the middlefold lines 113 and 123.

[0048] As a non-limiting example, the segments 158 a, 158 b and 168 a,168 b are inclined by about 15° relative to a line extendingtransversely to the longitudinal direction D, such that the dihedralangle formed between the pairs of segments 158 a, 158 b and 168 a, 168 bis about 150ø.

[0049] The generally planar film 100 together with its two Z-folds 110and 120 and provided with its two cutouts 150 and 160 as shown in FIGS.5 and 5a is preferably fed directly to a conventional form, fill, andseal machine for making bags.

[0050] Such machines are often referred to as “FFS” machines, from theinitials of the terms “form, fill, and seal”.

[0051] Numerous machines of this type have already been proposed.

[0052] Most such machines have: a forming throat which has an inputreceiving the film in the flat state and which has an output deliveringthe film shaped into a tube; a filling chute which opens out into theforming throat and consequently into the formed tube; longitudinalheat-sealing means for closing the tube longitudinally; and meanssuitable for acting sequentially to generate a first transverse line ofheat-sealing before material is inserted into the tube by means of thefilling chute, and then a second transverse line of heat-sealing oncethe material has been inserted into the tube, so as to close the bagaround thematerial.

[0053] The general structure of such machines is well known to theperson skilled in the art, so the structure is not described in detailbelow.

[0054] As mentioned above, according to an essential characteristic ofthe present invention, the male/female closure strips 170 are providedwith a control cursor 1710.

[0055] As illustrated on FIGS. 10, 12 and 13, preferably the male/femaleclosure strips comprise a male/profile 172 provided on a first main wall174 and a female profile 176 provided on a second main wall 178.

[0056] In a variant the male profile 172 and the female profile 176 maybe replaced by equivalent complementary hooked means.

[0057] The two main walls 174 and 178 are adapted to be fixed on thepackaging bag sheet 100.

[0058] According to a preferential embodiment of the invention, asillustrated on FIG. 10, the two main walls 174, 178 are initiallyconnected by an auxiliary wall 179. This auxiliary wall 179 is adaptedto be broken when the bag is opened the first time. Thus the auxiliarywall 179 is an evidence of an opening of the bag when it is broken.

[0059] Generally the cursor 1710 has two lateral flanges 1712, 1714interconnected by means of a web 1716 and which co-operate with anelongate central tongue 1718 placed between the closure strips 172, 176to define two converging passages 1720, 1722 for the interfittablecomplementary closure strips 172, 176. The central tongue 1718 extendsonly on a part of the cursor 1710. Thus, when the direction ofdisplacement of the cursor 1710 relative to the closure strips 172, 176tends to force the closure strips 172, 176 into engagement, the bag isclosed. In contrast, when the cursor 1710 is displaced in the oppositedirection, the bag is opened by means of the central tongue 1718separating the closure strips 172, 176.

[0060] It will be observed that in the context of the present invention,it is preferable for complementary male/female closure strips 170 to bedeposited on the film 100 in the vicinity of the mouth zone of a bagtransversely to the longitudinal direction D, and prior to the film 100being brought to the forming throat of the FFS machine, as shown in FIG.7

[0061] Still more precisely, closure strips 170 are placed against themain face 130 facing the cutouts 150 and 160, that is between thetransverse edges 156 and 158 at one end and 166 and 168 at the otherend.

[0062] The closure strips 170 are preferably of a length that is equalto the width of the main face 130, that is the distance between the foldlines 111 and 121.

[0063] After being placed on the film 100, the strips 170 are secured inposition on the film 100 by any appropriate means. Preferably, afterthey have been put into place, the strips 170 are initially fixed to thefilm 100 solely by means of their ends using a spot heat-sealingtechnique. The strips 170 are subsequently fixed to the main faces ofthe bag over the full length of their inside faces, preferably whenmaking the transverse lines of heat-sealing in the manner describedbelow with reference to FIG. 9. When the strips 170 are secured by spotheat-sealing at their ends, the lateral edges of the bag facing thefolds 110, 120 can also be secured by spot heat-sealing at the zoneswhere the transverse lines of heat-sealing shown in FIG. 9 willsubsequently be made for holding the above-mentioned folds together andpreventing them from deforming as the film 100 moves on.

[0064] Nevertheless, in a variant, at least one of the strips 170 may beheat-sealed to the film 100 along its entire length as soon as it is putinto place.

[0065] The above-mentioned means for spot heat-sealing are preferablyadjustable along the length of the film 100 so as to make it possiblefor them to be adjusted accurately relative to the desired length forthe bags and to the zones that will subsequently correspond to thetransverse lines of heat-sealing.

[0066] Naturally, it is also necessary to synchronize carefully theinstant at which the spot heat-sealing means are operated relative tothe travel of the film 100, since the instants at which the spotheat-sealing means operate determine both the locations of thecorresponding heat-sealing zones and the pitch of the zones.

[0067] By fixing the closure strips 170 by means of their ends, andpossibly also by fixing the folds 110 and 120 by spot heat-sealing,subsequent travel of the film 100 is made easier and it is also easierto subsequently perform the heat-sealing as shown in FIG. 9,particularly because of the resulting crushing of the ends of the strips170.

[0068] The means for making the above-mentioned spots of heat-sealingcan be generally like the means described in document FR-A-2 638 419.

[0069] In a variant, the closure strips 170 are fixed, and the folds 110and 120 are held temporarily by spots that are not made by heat-sealing,but are made by any equivalent means, such as by static discharge or byspots of adhesive.

[0070] The means designed for depositing the closure strips 170 on thefilm 100 so that they extend transversely to the longitudinal directionD of the film 100 can be implemented in numerous ways.

[0071] By way of non-limiting examples, these means may be like themeans described in the following documents: U.S. Pat. No. 4,617,683,U.S. Pat. Nos. 4,655,862, 4,666,536, 4,701,361, 4,709,398, 4,878,987,4,844,759, 4,929,225, 4,909,017, and U.S. Pat. No. 5,111,643.

[0072] Once the folds 110 and 120 have been made and the closure strips170 have been put into place and secured, at least temporarily, the filmassembly 100 as shown in FIG. 7 is sent to the forming throat of an FFSmachine, as mentioned above.

[0073] Where appropriate, special means may be provided at the formingthroat to facilitate passage thereover, in particular of the folds 110,120. By way of example, complementary windows may be provided on theforming throat to receive the folds 110 and 120.

[0074] On leaving the forming throat, the film 100 is shaped into atubular state, as shown in FIG. 8. The laterally outer free edges 141and 143 of the segments 140 and 142 are then brought together andheat-sealed in a conventional manner by the above-mentioned longitudinalheat-sealing means of the FFS machine.

[0075] The tubular film is then filled with its content by means of thefilling chute provided for this purpose.

[0076] The tubular film is then brought to face the heat-sealing meansprovided for making the lines of heat-sealing shown in FIG. 9.

[0077] The following are then preferably provided at these heat-sealingmeans:

[0078] two mutually parallel lines of heat-sealing 180 and 182; and

[0079] respective lines of heat-sealing 184 and 186 at the peripheriesof the cutouts 150 and 160.

[0080] One of the transverse lines of heal-sealing 180 coincides withthe transverse edges 156 and 166 of the cutouts. This transverse line ofheat-sealing 180 is designed to form the bottom of a bag. In the lateralbellows, it serves to connect together four thicknesses of film, thatis, the two main faces and the lateral bellows, and between the bellowsit connects together two thicknesses of film corresponding to the mainfaces.

[0081] The other transverse line of heat-sealing 182 is made between thetransverse edges 156, 158 and 166, 168 of the cutouts. This transverseline of heat-sealing 182 is designed to form the mouth of a bag. Itinterconnects the two main faces.

[0082] Once the lines of heat-sealing 180 and 182 have been made, atransverse rectilinear cut line 181 can be formed between them so as toseparate two adjacent bags.

[0083] The lines of heat-sealing 184 and 186 are respectively made up ofpairs of segments 184 a, 184 b and 186 a, 186 b respectively coveringthe longitudinal edges 152, 154 and 162, 164 and also the transverseedges 158 and 168 of the cutouts.

[0084] In this way, the lines of heat-sealing 184, 182, and 186intersect, thereby ensuring that the mouth of a bag is properly sealed.More precisely, the segments 184 a and 186 a connect together theoutside edges of the two main faces of the bag, while the segments 184 band 186 b connect together the edges 158 a, 158 b and the edges 168 a,168 b.

[0085] The method of the present invention has the fundamental advantageof limiting the lines of heat-sealing 184, 182, and 186 to twothicknesses of film, in particular where the closure strips 170 arefixed thereto, whereas most conventional methods need to performheat-sealing through four thicknesses of film at the lateral bellows.

[0086] Naturally, the present invention is not limited to the embodimentdescribed above, but extends to any variant coming within the spiritthereof.

[0087] For example, it is possible to make bags using a film of the typeshown in FIG. 7 having cutouts 150, 160 and closure strips 170, withoutapplying the film to a form, fill, and seal machine as mentioned above.The film can then be shaped to have a tubular state by any appropriateconventional means.

[0088] In the context of the present invention, the film 100 can bevaried in numerous ways. It is preferably constituted by a thermoplasticfilm. Nevertheless, the invention applies to any flexible film that canbe used for making a packaging bag.

[0089] Furthermore, the person skilled in the art will understand thatalthough, in the example shown in FIG. 5, the longitudinal edges 152,154, 162, and 164 of the cutouts 150 and 160 coincide with the foldlines 111, 115, 121, and 125, so that the lines of heat-sealing 184 aand 186 a are made on two thicknesses of film, when the longitudinaledges 152, 154, 162, 164 of the Cutouts 150 and 160 are set back fromthe fold lines 111, 115, 121, and 125, then the lines of heat-sealing184 a and 186 a are made, at least in part, on four superposedthicknesses of film. The same applies for end portions of the transverselines of heat-sealing 180 and 182. The lines of heat-sealing 184 a and186 a may also be made at least in part so as to be set back from thefold lines 111, 115, 121, and 125, as shown in FIG. 9. The variantembodiment of the cutouts as shown in FIG. 5a makes it possible toimprove the lateral sealing of the bags.

[0090] Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claim, thepresent invention may be practiced otherwise than as specificallydescribed herein.

1. A method of manufacturing packaging bags comprising the steps of:providing a packaging bag sheet, having a longitudinal extent, forforming a packaging bag; folding said packaging bag sheet so as to forma pair of laterally spaced bellow regions within side edge portions ofsaid packaging bag sheet; forming cutouts within each one of said pairof laterally spaced, bellow regions of said packaging bag sheet so thatsaid bag has only two sheet thicknesses superposed with respect to eachother within a mouth region of said bellows; placing complementarymale/femelle closure strips provided with a control cursor upon saidpackaging bag sheet within the vicinity of said mouth region of said bagand transversely with respect to said longitudinal feeding direction;and heat-sealing edges portions of said sheet to edge portions of saidcutouts so as to close and seal said bag.
 2. A method according to claim1 , wherein said cursor has two lateral flanges interconnected by meansof a web and which co-operate with an elongate central tongue placedbetween the closure strips to define two converging passages for theclosure strips.
 3. A method according to claim 1 , wherein the closurestrips are provided on respective main support walls which are adaptedto be fixed on the packaging bag sheet and which are connected togetherby an auxiliary wall adapted to be broken when the bag is opened thefirst time.
 4. A method according to claim 1 , further comprising thesteps of: feeding said packaging bag sheet in a direction parallel tosaid longitudinal extent of said packaging bag sheet; and forming saidpair of laterally spaced bellow regions by making two Z-folds whichextend parallel to said longitudinal feeding direction of the saidpackaging bag sheet.
 5. A method according to claim 4 , wherein: eachone of said Z-folds is formed by a pair of blades that are partiallysuperposed with respect to each other so as to partially overlap eachother and thereby form a baffle within which a side edge portion of saidpackaging bag sheet is engaged.
 6. A method according to claim 4 ,wherein: said cutouts are formed within said pair of laterally spacedbellow regions after said folds have been formed within said packagingbag sheet so as to form said pair of laterally spaced bellow regions. 7.A method according to claim 4 , wherein: said cutouts are formed withinsaid pair of laterally spaced bellow regions before said folds areformed within said packaging bag sheet so as to form said pair oflaterally spaced bellow regions.
 8. A method according to claim 5 ,wherein: said cutouts are formed within said pair of laterally spacedbellow regions by using one of said pair of fold-forming blades as ananvil for a cutting-out punch thereby leaving one of the faces of saidpackaging bag sheet intact.
 9. A method according to claim 1 , furthercomprising the step of: initially holding said complementary closurestrips in position upon said packaging bag sheet by spot heat-sealingends of said closure strips to said packaging bag sheet.
 10. A methodaccording to claim 4 , further comprising the step of: fixing saidZ-folds by spot heat-sealing said Z-folds at zones where transverselines of heat-sealing are to be formed so as to close said bag.
 11. Amethod according to claim 10 , wherein said formation of said transverselines of heat-sealing comprises the step of: forming two mutuallyparallel transverse lines of heat-sealing such that one of saidtransverse lines of heat-sealing forms the bottom of a bag while theother one of said transverse lines of heat-sealing forms the mouth of abag.
 12. A method according to claim 11 , further comprising the stepof: forming a rectilinear cut line between said two transverse lines ofheat-sealing so as to separate said formed packaging bag into twoseparate adjacent bags.
 13. A machine for manufacturing packaging bagsfrom packaging bag sheets, comprising: means for feeding a packaging bagsheet having a longitudinal extent; means for folding said packaging bagsheet so as to form a pair of laterally spaced bellow regions withinside edge portions of said packaging bag sheet; means for formingcutouts within each one of said pair of laterally spaced bellow regionsof said packaging bag sheet such that said packaging bag has only twosuperposed sheet thicknesses within a mouth region of said bellows;means for placing complementary male/femelle closure strips providedwith a control cursor upon said packaging bag sheet within the vicinityof said mouth region of said bag such that said closure strips extendtransversely with respect to said longitudinal extent of said packagingbag sheet;and means for heat-sealing together edges portions of saidpackaging bag sheet to edge portions of said cutouts so as to close andseal said bag.
 14. A machine according to claim 13 wherein said cursorhas two lateral flanges interconnected by means of a web and whichco-operate with an elongate central tongue placed between the closurestrips to define two converging passages for the closure strips.
 15. Amachine according to claim 13 wherein the closure strips are provided onrespective main support walls which are adapted to be fixed on thepackaging bag sheet and which are connected together by an auxiliarywall adapted to be broken when the bag is opened the first time.
 16. Amachine according to claim 13 , further comprising: means for formingsaid pair of laterally spaced bellow regions so as to comprise a pair ofZ-folds which extend parallel to said longitudinal extent of saidpackaging bag sheet.
 17. A machine according to claim 16 , wherein: saidmeans for forming said pair of laterally spaced bellow regions comprisestwo partially superposed blades that overlap each other and thereby forma baffle into which said packaging bag sheet is engaged so as to formsaid pair of Z-folds.
 18. A machine according to claim 17 , furthercomprising: a cut-out punch; and one of said fold-forming bladescomprises an anvil for said cut-out punch when said cut-out punch isused to make said cutouts so as to leave one of the faces of saidpackaging bag sheet intact.
 19. A machine according to claim 13 ,wherein: said machine comprises a form, fill, and seal machine.
 20. Amachine according to claim 19 , wherein said form, fill, and sealmachine comprises: a forming throat having an inlet that receives saidpackaging bag sheet in a planar state, and an outlet that delivers saidpackaging bag sheet shaped into a tube, a filling chute which opens outinto said forming throat and consequently into said tube so as todeposit material into said tube, longitudinal heat-sealing means forclosing and sealing said tube longitudinally, and means for sequentiallygenerating transverse lines of heat-sealing so as to close and seal saidformed bag.
 21. A machine according to claim 13 , further comprising:means for initially securing said closure strips in position upon saidpackaging bag sheet by spot heat-sealing ends of said closure strips tosaid packaging bag sheet.
 22. A machine according to claim 16 , furthercomprising: means for fixing said Z-folds by spot heat-sealing saidZ-folds at zones that are subsequently to include transverse lines ofheat-sealing so as to close and seal said bag.
 23. A machine accordingto claim 22 further comprising: heat-sealing means for forming twomutually parallel transverse lines of heat-sealing such that one of saidtransverse line of heat-sealing forms the bottom of a bag while theother one of said transverse lines of heat-sealing forms the mouth of abag.
 24. A machine according to claim 23 , further comprising: means forforming a rectilinear cut line between said two transverse lines ofheat-sealing so as to separate said formed packaging bag into twoseparate adjacent bags.
 25. A packaging bag comprising: a foldedpackaging sheet, having a longitudinal extent, for forming a packagingbag; a pair of laterally spaced bellows formed within side edge portionsof said folded packaging bag sheet; cutout portions respectively formedwithin each one of said pair of laterally spaced bellows so that saidpackaging bag has only two sheet thickness superimposed with respect toeach other within a mouth region of said bag; complementary male/femaleclosure strips provided with a control cursor upon said packaging bagsheet within the vicinity of said mouth region of said bag such thatsaid closure strips extend transversely with respect to saidlongitudinal exent of said packaging sheet; and heat-sealed regions forclosing and sealing said packaging bag.
 26. A bag according to claim 25, wherein: said heat-sealed regions of said packaging bag comprises aline of heat-sealing defined between edge portions of said packaging bagsheet and edge portions of said cutouts.
 27. A packaging bag as setforth in claim 25 , wherein said packaging bag sheet comprises: a planarmain face; first longitudinal flaps disposed upon and integrallyconnected to opposite sides of said planar main face; secondlongitudinal flaps disposed upon and integrally connected to oppositesides of said first longitudinal flaps, and auxiliary segments disposedupon and integrally connected to said second longitudinal flaps.
 28. Apackaging bag as set forth in claim 25 , wherein: each cutout portion isdefined by two rectilinear longitudinal edges coinciding respectivelywith outer definition lines of said laterally spaced bellows, arectilinear transverse edge extending transversely to said longitudinalextent of said packaging bag sheet, and a second transverse edge that isnot rectilinear and is concave towards said mouth region of said bag.29. A packaging bag as set forth in claim 25 , wherein: each cutoutportion is defined by two rectilinear longitudinal edges which arerespectively set back from the outer definition lines of said laterallyspaced bellows, a rectilinear transverse edge extending transversely tosaid longitudinal extent of said packaging bag sheet, and a secondtransverse edge that is not rectilinear and is concave towards saidmouth region of said bag.
 30. A packaging bag as set forth in claim 28 ,wherein: said second transverse edge comprises a dihedral made up of tworectilinear segments.
 31. A packaging bag comprising: a folded packagingsheet, having a longitudinal extent, for forming a packaging bag; a pairof laterally spaced bellows formed within side edge portions of saidfolded packaging bag sheet; cutout portions respectively formed withineach one of said pair of laterally spaced bellows so that said packagingbag has only two sheet thickness superimposed with respect to each otherwithin a mouth region of said bag; complementary male/female closurestrips provided with a control cursor upon said packaging bag sheetwithin the vicinity of said mouth region of said bag such that saidclosure strips extend transversely with respect to said longitudinalexent of said packaging sheet; and heat-sealed regions for closing andsealing said packaging bag, each one of said cutout portions beingdefined by two rectilinear longitudinal edges coinciding respectivelywith outer definition lines of said laterally spaced bellows, arectilinear transverse edge extending transversely to said longitudinalextent of said packaging bag sheet, and a second transverse edge that isnot rectilinear and is concave towards said mouth region of said bag.32. A packaging bag comprising: a folded packaging sheet, having alongitudinal extent, for forming a packaging bag; a pair of laterallyspaced bellows formed within side edge portions of said folded packagingbag sheet; cutout portions respectively formed within each one of saidpair of laterally spaced bellows so that said packaging bag has only twosheet thickness superimposed with respect to each other within a mouthregion of said bag; complementary male/female closure strips providedwith a control cursor upon said packaging bag sheet within the vicinityof said mouth region of said bag such that said closure strips extendtransversely with respect to said longitudinal event of said packagingsheet; and heat-sealed regions for closing and sealing said packagingbag, each one of said cutout portions being defined by two rectilinearlongitudinal edges which are respectively set back from the outerdefinition lines of said laterally spaced bellows, a rectilineartransverse edge extending transversely with respect to said longitudinalextent of said packaging bag sheet, and a second transverse edge that isnot rectilinear and is concave towards said mouth region of said bag.33. A bag according to claim 32 , wherein: said heat-sealed regions ofsaid packaging bag comprises a line of heat-sealing defined between edgeportions of said packaging bag sheet and edge portions of said cutoutportions.
 34. A packaging bag as set forth in claim 32 , wherein saidpackaging bag sheet comprises: a planar main face; first longitudinalflaps disposed upon and integrally connected to opposite sides of saidplanar main face; second longitudinal flaps disposed upon and integrallyconnected to opposite sides of said first longitudinal flaps, andauxiliary segments disposed upon and integrally connected to said secondlongitudinal flaps.
 35. A packaging bag as set forth in claim 32 ,wherein: said second transverse edge comprises a dihedral made up of tworectilinear segments.